Web sites up and running despite denial of service threat

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SEATTLE — Microsoft Corp. said it had fought off an attempted software virus attack Tuesday that was aimed at shutting down some of the company’s Web sites.

Stephen Toulouse, a security program manager for Microsoft, said the company’s Web sites were up and running as of midmorning.

The virus works by getting infected computers to send hundreds of thousands of requests for the site per minute, in hopes of crippling it. Toulouse would not detail how the company had been able to ward off the attack, citing security concerns.

“It’s still a little early and we remain vigilant,” he said.

The virus, called “Mydoom.B,” was programmed to launch an attack on Microsoft’s site Tuesday, two days after a variant shut down the Web site of The SCO Group, a small Utah software company.

But security experts had said the Mydoom.B variant was spreading much less quickly than Mydoom.A, the version that attacked SCO Group.

Microsoft said that computers infected with the virus would not be able to access Microsoft’s Web site. The Redmond, Wash.-based company has set up an alternative Web site, https://information.microsoft.com, for those users. (MSNBC is a Microsoft - NBC joint venture.)

Last week, Microsoft said it would to pay $250,000 to anyone who helps authorities find and prosecute the author of the virus. The cash reward is the third so far under a $5 million program Microsoft announced in early November to help U.S. authorities catch authors of unusually damaging Internet infections aimed at consumers of the company’s software products.

SCO Group had previously offered a $250,000 reward for information leading to the arrest and conviction of the creator of the Mydoom.A version.